The invention relates to 4,6-bis-trichloromethyl-s-triazines which are substituted in the 2-position and to a light-sensitive composition containing these compounds.
Compounds of the above-mentioned type are known for use as initiators for a number of photochemical reactions. They are employed, on the one hand, to utilize the free radicals formed under the action of actinic radiation for triggering polymerization reactions or color changes and, on the other hand, to initiate secondary reactions by means of the freed acid.
DE-C 22 43 621 (=U.S. Pat. No. 3,954,475) describes styryl-substituted trichloromethyl-s-triazines exhibiting a number of advantageous properties. However, it is a disadvantage of these compounds that their preparation is relatively complicated.
DE-C 27 18 259 (=U.S. Pat. No. 4,189,323) discloses 2-aryl-4,6-bis-trichloromethyl-s-triazines with polynuclear aryl groups, which have comparably good properties, in particular, a high sensitivity to light and which can be prepared by simpler methods. They are obtained by cotrimerization of trichloroacetonitrile with aromatically substituted acetonitriles, in a yield which is fairly high for this type of reaction. Certain amounts of by-products are, however, invariably formed, which must be separated from the desired compound.
Furthermore, DE-B 27 17 778 discloses light-sensitive compositions on a basis of unsaturated compounds or polymeric azides, which contain 2-heteroylcarbonylmethylenebenzothiazoles or -benzoselenazoles as sensitizers.
DE-A 25 51 641 describes photopolymerizable compositions which contain photoinitiators comprising a combination of particular trihalomethyl-s-triazines with acylmethylene heterocycles, for example, benzoylmethylene benzothiazolines.
EP-A 135 348 and EP-A 135 863 disclose 1-alkyl-2-carbonylmethylene-benzothiazoles and similar heterocycles for use as photoinitiators, which carry a trichloromethylphenyl group on the carbonyl group.
DE-A 37 26 001 describes photopolymerizable compositions containing, as photoinitiators, bis-trihalomethyl-s-triazinylbenzenes which are further substituted by an amino group. The sensitivity of these compositions can be enhanced by adding sensitizers, such as Michler's ketone or benzoylene-ethylene-benzothiazoles.
EP-A 137 452 describes 2-(styrylphenyl)-4,6-bis-trichloromethyl-s-triazines as photoinitiators and photolytically activable acid donors.
German patent application P 38 07 381.1 of earlier date proposes similar compounds containing bis-trichloromethyl-s-triazine groups which form the external substituents on an aroylmethylene heterocycle.
Most of these compounds acting as photoinitiators are prepared by way of relatively complicated syntheses. Virtually all trichloromethyl-s-triazine derivatives which are customarily preferred due to their high activity are obtained by the above-mentioned method of cotrimerization of trichloroacetonitrile with other nitriles. It is, above all, the objective of the recent development of technology to provide well-known satisfactorily acting compounds or similar compounds by way of syntheses producing less by-products, the ecologically safe disposal of which gives rise to increasingly serious problems, as is known.